Re: [PATCH 1/2] mtd: use put_device() if device_register fail

[arvindY]

On Wednesday 14 March 2018 08:06 PM, Boris Brezillon wrote:
> On Fri,  9 Mar 2018 16:20:48 +0530
> Arvind Yadav <arvind.yadav.cs@xxxxxxxxx> wrote:
>
> > if device_register() returned an error! Always use put_device()
> > to give up the reference initialized.
> >
> > Signed-off-by: Arvind Yadav <arvind.yadav.cs@xxxxxxxxx>
> > ---
> >   drivers/mtd/mtdcore.c | 1 +
> >   1 file changed, 1 insertion(+)
> >
> > diff --git a/drivers/mtd/mtdcore.c b/drivers/mtd/mtdcore.c
> > index 28553c8..4d77ca2 100644
> > --- a/drivers/mtd/mtdcore.c
> > +++ b/drivers/mtd/mtdcore.c
> > @@ -586,6 +586,7 @@ int add_mtd_device(struct mtd_info *mtd)
> >   	return 0;
> >   
> >   fail_added:
> > +	put_device(&mtd->dev);
> Not sure this is a good idea: the put_device() call will trigger
> an mtd_devtype->release(), which will in turn call device_destroy() on
> something that does not exist yet. Not sure if this is a real problem,
> but it does not look like the right thing to do.
yes, you are correct. No need to call put_device().
which can cause other problem.

> >   	of_node_put(mtd_get_of_node(mtd));
> You're referencing an object that is supposed to have been
> freed/released by the put_device() call. Again, it's not really a
> problem because in our case ->release() does not free the mtd object
> (as is usually done in other parts of the kernel), but it still looks
> wrong. It's probably better to move the of_node_put() and the below
> idr_remove() call in the ->release() hook if you want to use
> put_device().
>
> >   	idr_remove(&mtd_idr, i);
Sure, we can move put_device() below this. But need to check
how we can add hook in release.
> >   fail_locked:
~arvind